Where are the begin() and end() functions defined in C++?

Question

In cppreference.com, it states that the begin() and end() functions are defined in the header file < iterator >. But I still can use the begin() and end() functions without including the < iterator > header. I wonder why? Is it because I use;

using namespace std;

So it is included?

No, using namespace xxx doesn't include any header files. It only means that you can write begin() instead of std::begin(). The `<iterator> header must be included through some other header that you did include into your .cpp. — Violet Giraffe
– Violet Giraffe, Commented Feb 25, 2016 at 7:07
Unrelate to answer: Avoid writing using namespace std; in real code. — Mohit Jain
– Mohit Jain, Commented Feb 25, 2016 at 7:10

Niall · Accepted Answer · 2016-02-25 07:10:39Z

9

Read from notes on the same page:

In addition to being included in <iterator>, std::begin is guaranteed to become available if any of the following headers are included: <array>, <deque>, <forward_list>, <list>, <map>, <regex>, <set>, <string>, <unordered_map>, <unordered_set>, and <vector>.

Apart from these list of headers, std::begin may get included from some other header also.

edited Feb 25, 2016 at 7:10

Niall

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answered Feb 25, 2016 at 7:08

Mohit Jain

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1 Comment

BVBC Over a year ago

Oh, ok, I didn't see that. That make so much more sense.

Violet Giraffe · Accepted Answer · 2016-02-25 07:07:48Z

1

No, using namespace xxx doesn't include any header files. It only means that you can write begin() instead of std::begin(). The <iterator> header must be included through some other header that you did include into your .cpp.

answered Feb 25, 2016 at 7:07

Violet Giraffe

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